Scope
This section covers structural steelwork and cold-rolled steel purlins and girts.
For light gauge steel framing for domestic houses, refer to Specification for
Wall Roof and Floor Framing.
Relevant Standards
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- AS 4100 Steel structures
- AS/NZS 4600 Cold-formed steel structures
- AS 2327.1 Composite structures – Simply supported beams
- AS 1163 Structural steel hollow sections
- AS/NZS 1594 Hot-rolled steel flat products
- AS/NZS 3678 Structural steel - Hot-rolled plates, floorplates and slabs
- AS/NZS 3679.1 Structural steel Part 1: Hot-rolled bars and sections
- AS/NZS 3679.2 Structural steel Part 2: Welded I sections
- AS 1110 ISO metric hexagon precision bolts and screws
- AS 1111 ISO metric hexagon commercial bolts and screws
- AS 1112 ISO metric hexagon nuts, including thin nuts and washers for structural engineering
- AS/NZS 1252 High strength steel bolts with associated nuts and washers for structural engineering
- AS/NZS 1559 Hot-dip galvanised steel bolts with associated nuts and washers for tower construction
- AS/NZS 1554 Structural steel welding
- AS 1275 Metric screw threads for fasteners
- AS 1237.1 Plain washers for metric bolts, screws and nuts for general purposes
- AS/NZS 4291.1 Mechanical properties of fasteners, made of carbon steel and alloy steel, Part 1: bolts, screws, studs
- AS/NZS 4291.2 Mechanical properties of fasteners, Part 2: Nuts with specified proof load values –coarse thread
- AS 1397 Steel sheet and strip
- AS 1627 Metal finishing - preparation and pre-treatment of surfaces
- AS/NZS 4680 Hot-dip galvanised (zinc) coatings on fabricated ferrous articles
- AS/NZS 2312 Guide to the protection of structural steel against exterior atmospheric corrosion by use of protective coatings
- AS 1627.4 Metal finishing - Abrasive blast cleaning
- AS 1627.5 Metal finishing - Pickling, descaling and oxide removal
- AS/NZS 3750.1 Paints for steel structures - Part 1 Epoxy mastic (two-pack)
- AS/NZS 3750.13 Paints for steel structures - Part 13 Epoxy primer (two-pack)
- AS/NZS 3750.14 Paints for steel structures - Part 14 High-build epoxy (two-pack)
- AS/NZS 3750.15 Paints for steel structures - Part 15 Inorganic zinc silicate paint
Commencement
Fabrication shall commence as soon as practical after, but not before, the Builder has issued:
- a written order
- the relevant contract drawings, specifications and schedule of work
- written approval of any details provided by the Contractor
- Erection shall commence as soon as practical after, but not before the supporting structure has been constructed.
Fabrication and Erection
- All fabrication and erection of structural steelwork shall comply with AS 4100, BCA Section 6.6 & IS 800 and the standards referred to therein.
- Welding shall be SP and comply with AS/NZS 1554, IS 6419. All welds shall be 6 mm continuous fillet unless noted otherwise. Full penetration butt welds are required on all plates over 12 mm in thickness.
- All bolts and nuts, except high strength friction grip bolts, shall be snug tightened as per AS/NZS 1252, IS 1367.
- High strength friction grip bolts shall be tensioned to the recommended values as per AS/NZS 1252, IS 1367.
- All seal plates on hollow sections shall be provided with a breather hole to permit hot dip galvanising.
- All purlins, girts, fascias, associated bridging and accessories shall be installed in accordance with the manufacturer’s recommendations.
Materials
Inspections and Tests
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The following fabrication and erection inspections shall be performed.
Structural Steelwork Fabrication
| Item or Product | Inspection Required | Accept Criteria | Hold / Witness
|
| Drawings & Specifications | Inspect controlled documents | Controlled copy of latest issue on site | Hold
|
| Steel section | Check marked length before cutting | +,- 2 mm * | Hold
|
| Holes in steel sections | Check marking of position & diameter | +,- 2 mm * Holes to be 2 mm larger than nominal bolt size. | Hold
|
| Plates | Check marking of dimensions | +,- 2 mm * | Hold
|
| Holes, cut-outs in plates | Check marking of position & diameter | +,- 2 mm * | Hold
|
| Fabricate all items | Check length, check orientation | +,- 2 mm * | Hold
|
| Welding | Visual | Continuous or as specified | Hold
|
| Surface treatment | Visual | As specified, no unpainted areas | Hold
|
| Identification marks | Visual | Clear & as specified | Hold
|
| HD Bolt kits | Visual | Bolts, nuts, washers included | Witness
|
| Touch up painting | Visual | No chipped or damaged paint | Witness
|
| Loading of transport for delivery to site | Count of all items | All items loaded | Hold
|
| Delivery and unloading on site | Count of all items | All items unloaded | Hold
|
| Notes
|
| All tolerances shall be in accordance with AS 4100.
|
| The general tolerance is +,- 2 mm (*), although there are some specific tolerances including cross section, compression members, beams and tension members. |
Structural Steelwork Erection
| Item or Product | Inspection Required | Accept Criteria | Hold / Witness
|
| Drawings & Specifications | Inspect controlled documents | Controlled copy of latest issue on site | Hold
|
| Principal steel sections | Spot check | As specified | Witness
|
| Shop surface treatment | Visual before erection | No major blemishes | Witness
|
| Holding down bolts | Bolt grade
Bolt diameter
Bolt length
Bolt centres in each group
Bolt group centres of adjacent groups
Accumulated length
Bolt group centres to column centre line | As specified
As specified
+,- 3 mm
+,- 3 mm
+,- 6 mm
+,- 6 mm/30 m,
+,- 25 mm
+,- 6 mm | Hold
|
| Column base position | Spot check | +,- 6 mm | Witness
|
| Column base level | Spot check | +,- 10 mm | Witness
|
| Column base contact | Spot check | Full contact | Witness
|
| Compression member plumb from base position (Up to 60 m high) | Spot check | Height/500, 25 mm | Witness
|
| Compression member plumb from base position (Over 60 m high) | Spot check | 25 + (H-60)/3000, 50 mm | Witness
|
| Compression member storey deviation | Spot check | Height/500 | Witness
|
| Column splice level | Spot check | +,- 10 mm | Witness
|
| Column splice position | Spot check | See compression member plumb | Witness
|
| Column splice plan position | Spot check | +,- 2 mm | Witness
|
| Beam connections | Spot check | Completed | Witness
|
| Beam sweep | Spot check | Braced length/500 | Witness
|
| Beam position at connection | Spot check | +,- 10 mm | Witness
|
| Beam web | Spot check | +,- 3 mm | Witness
|
| Tension member position | Spot check | +,- 3 mm | Witness
|
| Overall building dimensions | Spot check | AS 4100 | Witness
|
| Connections | Spot check | As specified | Witness
|
| Touch up surface treatment | Visual | No visible defects or chipping | Witness
|
| Grout packs at supports | Visual | In place.
Material complies to AS 3600 | Witness
|
| Notes
|
| All tolerances shall be as shown, except where overridden by AS 4100. |
Potential Problems and Solutions
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General
Because structural steelwork is prefabricated and bolted together on site, small changes in the building details at either design or construction stages can result in the inability of the steelwork to fit together.
Shop Drawings
Steel fabricators, working in a workshop remote from the site, require sufficient information to accurately produce the steelwork. Prepare shop drawings showing all dimensions of sections, holes, bolts etc from the engineers and architects details.
Interface with Other Materials
Structural steelwork must support and be supported by other parts of the building in close contact. A failure to visualise the superposition of each component can lead to construction that is not in accordance with the designer’s intention or could necessitate modifications to the steelwork. Prepare details of how the brickwork, timber, windows and flashings are to be built around the steelwork. Before erection commences, inspect and confirm the location in the building, particularly provision for supporting columns.
Site Modifications
When erecting prefabricated steelwork, errors in previous construction will become apparent and it will be necessary to make modifications. On completion of repairs, the weld spatter and dags must be removed, welds chipped and the steelwork paint system repaired to achieve the original protection.
Column Support
On completion of erection, tighten all holding-down bolts and grout under column bases.
Protection against Corrosion
If steel column or posts are used, they must be protected against corrosion originating from ground water or from the atmosphere. They should be galvanised and, where appropriate, painted. Steel posts must be supported clear of the ground. If steel posts are embedded in concrete footings, the concrete must be built up clear of the surrounding ground level to prevent attack by salt-rich ground water.
Bracing
Steel posts for houses, deck or roofs should incorporate diagonal bracing to prevent side sway.
